Time-of-Flight Mass Spectrometer Variable Ion Focusing
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Solution Overview
Problem
Time-of-flight mass spectrometers face challenges in maintaining high mass resolution and ion transmission due to space charge effects, particularly with multiply charged ions and high ion densities, which lead to reduced mass resolution and ion transmission.
Innovation Solution
A time-of-flight mass spectrometer with a variable voltage supply that adjusts ion focusing based on the charge state and number of ions, optimizing voltages to reduce space charge effects by controlling spatial dispersion, using a controller to determine optimal voltages from charge state and peak abundance data, and employing calibration procedures to establish voltage dependencies for different ion species.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If ion focusing arrangement uses fixed voltage, then device complexity is reduced, but mass resolution deteriorates due to space charge effects in high ion density packets
Solution Approach 1:
The patent applies dynamics by transitioning from fixed voltage to variable voltage control in the ion focusing arrangement. The voltage is dynamically adjusted based on the charge state and ion density of incoming ion packets, allowing the system to adapt to varying space charge conditions and maintain optimal mass resolution across different ion types.
Solution Approach 2:
The patent implements parameter changes by varying the voltage applied to the ion focusing arrangement according to the specific charge state and ion density of each ion packet. This parameter adjustment compensates for space charge effects, preventing ion packet dispersion and maintaining high mass resolution without requiring overly complex additional hardware.
2Measurement precision
If ion focusing strength is increased, then spatial dispersion is reduced, but space charge effects are enhanced due to higher charge density concentration
Solution Approach 1:
The patent uses parameter changes to adjust the voltage in the ion focusing arrangement based on the charge state and ion density of each packet. This allows optimization of focusing strength for each ion type, achieving sufficient spatial dispersion control while avoiding excessive focusing that would concentrate space charge effects and degrade performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances mass resolution and ion transmission by minimizing space charge effects, allowing for improved separation of ions with varying charge states and densities, thereby maintaining high mass resolution and tolerance to space charge.
Implementation Method 1
an ion focusing arrangement located between the ion injector and the detector for focusing the ion beam in at least one direction orthogonal to the ion path
Implementation Method 2
ion energy distributions and space charge interactions can cause ions to spread out in flight
Implementation Method 3
short ion pulses are generated by a pulsed ion injector to form an ion beam
Data Source
AI summary
A time-of-flight (ToF) mass spectrometer, comprising: a pulsed ion injector for forming an ion beam that travels along an ion path; a detector for detecting ions in the ion beam that arrive at the detector at times according to their m/z values; an ion focusing arrangement located between the ion injector and the detector for focusing the ion beam in at least one direction orthogonal to the ion path; and a variable voltage supply for supplying the ion focusing arrangement with at least one variable voltage that is dependent on a charge state and/or an amount of ions of at least one species of ions in the ion beam. A corresponding method of mass spectrometry is provided. The charge state and/or an amount of ions may be acquired from a pre-scan, or predicted. Tuning of the spectrometer based on a charge state and/or an amount of ions of at least one species of ions in the ion beam may be performed on the fly.